Electrical discharge tube



Sept. 4, 1956 E, FENNER l-rALl 2,761,992

ELECTRICAL DISCHARGE TUBE Filed Aug. 8, 1951 United vStates Patent O ELECTRICAL DISCHARGE TUBE Eckhard Fenner and Adolf Schmidt, Erlangen, Germany, asslgnors to Siemens-Reiniger-Werke Aktiengesellschaft, Erlangen, Germany, a corporation of Germany Application August 8, 1951, Serial No. 240,947 Claims priority, application Germany August 19, 1950 3 Claims. (Cl. 313-282) This invention is concerned with an electrical discharge tube, and especially with an X-ray tube, and is particularly concerned with the mounting of an electrode in such tube.

It is known to secure in electrical discharge tubes each of several electrodes at a different point of the tube envelope, which may be a glass envelope. For example, in the case of X-ray tubes, the cathode system may be secured on the so-called cathode extension of the envelope, and the anode system may be secured on the anode extension thereof. It is difficult in such tubes to adjust the electrodes in their proper positions during the assembly of the structure and to secure them against displacement from their positions relative to one another during the subsequent degassing of the metallic parts, which also causes considerable heating of the envelope wall. Another disadvantage resides in difficulties attending the cooling of the electrodes.

The invention overcomes these diiculties by securing at least one of the electrodes on the outside wall of a tubular metallic member made of chrome iron, Kovar or another metal, which fuses well with the glass envelope and forms part of the envelope of the tube, such member extending axially inwardly of the tube from a reentrant portion of the envelope, and providing on the inside of such member fastening or holding means such, for example, as a thread, a bayonet joint or the like. A suitable tool may then be used to engage the. fastening or holding means for the purpose of facilitating the positional adjustment of the corresponding electrode.

The tubular metallic member provides for a better cooling than the glass envelope wall, which is of considerable importance during the production of the tube as well as during its operation. The fastening or holding means, which is disposed on the inside of the metallic member, may be provided with auxiliary cooling means, e. g., with a cooling body or with suitable inlet and outlet means for a cooling medium.

The working of metals, which are adapted for fusing with glass, is relatively difficult. The invention therefore provides, at least on the inside of the tubular metallic member, an element of a metal which is easily worked, e. g., an iron element, and provides on the latter the fastening means.

The objects indicated above and further objects and features will appear from the description which is rendered below with reference to the single ligure in the accompanying drawing showing in diagrammatic manner, partly in elevation and partly in longitudinal section, as an example of the invention, a rotary anode X-ray tube.

Referring now to the drawing, numeral 1 indicates the envelope of the tube. Numeral 2 is the anode disk of the rotary anode system. All other parts of the anode system have been omitted to avoid encumbering the drawing. The cathode system comprises the cathode disk having the parts 3 and 4 and the lament 5 which is surrounded by the focusing means 6. The cathode disk parts 3 and 4 are carried by the cylindrical member 7. This cylindrical member may in known structures be secured on the inwardly directed reentrant envelope extension 9. In accordance with the invention, the member '7 is removably secured, e. g., by means of screws, as shown, to an annular, ringlike iron member 8 which in turn is held on the outside wall of the tubular metallic member 1t). The latter may be made, e. g., of chrome iron, and one of its ends is fused into the reentrant envelope portion 9. The tubular member 10 thus forms part of the envelope of the tube. On the inside wall of the tubular member 10 is disposed a metallic ring, e. g., an iron ring 11, which is provided with fastening or holding means, for example, with an interior thread. ri`he ringlike members 8 and 11 are permanently connected with the tubular member 10 in good heat-conducting relationship therewith, e. g., by brazing. The portion of the envelope carrying the glass seal 12 seals the other end of the tubular member 10 in vacuum tight manner. The current conductors 13 for the filament 5 extend through the glass seal 12.

A desired and suitable tube, e. g., a metal tube (not shown), may be threaded into the ring 11 for adjusting the position of the electrode during the assembly of the structure. Such metal tube may also be used for firmly holding the structure during the mounting thereof in a housing or in assembly with other parts. Finally, means may be secured to the ringlike member 11 for circulating a cooling medium through the structure during certain manufacturing phases as well as during the operation thereof.

Changes may be made within the scope and spirit of the appended claims.

We claim:

l. In an electric discharge tube comprising an envelope having a rst glass portion forming at one end thereof a tubular axially inwardly extending reentrant portion and having a metallic tubular mounting member fused at one of its ends to said reentrant portion and forming a continuation of said reentrant portion, said metallic tubular mounting member being made of a metal which fuses easily with glass but which is relatively difficult to machine, and having a second glass portion sealed to the other end of said metallic tubular mounting member and current conductors extending through said second glass portion; a fastening device comprising a first metallic ringlike member carried by said metallic tubular mounting member on the outside thereof and a second metallic ringlike member carried by said metallic tubular mounting member on the inside thereof, each said first and said second rinklike member being substantially permanently secured to said metallic tubular mounting member by being fused thereto and said ringlike members being made of a metal which is adapted to be relatively easily machined, a cylindrical holder secured to said first metallic ringlike member and axially extending therefrom, and electrode elements carried by said cylindrical holder, said second metallic ringlike member being provided with separable coupling means accessible externally of said envelope through said reentrant portion for receiving, first, an element for holding said discharge tube, and for receiving, second, means for conducting a cooling medium to said tube.

2. The structure defined in claim 1, wherein said cylindrical holder is removably secured to said rst metallic ringlike member.

3. The structure' defined in claim 1, wherein said metallic tubular mounting member is made of chromium-containing metal and whereinv said ringlike members are made of iron.

UNITED STATES PATENTS B01 May 6, 1930 Bouwers Sept. 22, 1931 Muller Oct. 31, 1933 Atlee Oct. 28, 1941 Knochel Mar. 24, 1942 Du Mond July 21, 1942 Schwarzer June 6, 1944 Horsley Sept. 20, 1949 

